Many of these reviews reported following published guidelines such as PRISMA or MOOSE, yet only half appropriately addressed publication bias in their reviews. Compared with previous research, our study found fewer reviews assessing publication bias and greater likelihood of publication bias among reviews not performing these evaluations.

SummaryThe validity of primary study results included in systematic reviews plays an important role in drawing conclusions about intervention effectiveness and carries implications for clinical decision-making. We evaluated the prevalence of methodological quality and risk of bias assessments in systematic reviews published in the five highest-ranked anaesthesia journals since 2007. The initial PubMed search yielded 315 citations, and our final sample after screening consisted of 207 systematic reviews. One hundred and seventy-four reviews conducted methodological quality/risk of bias analyses. The Jadad scale was most frequently used. Forty-four of the 83 reviews that included high risk of bias studies re-analysed their data omitting these trials: 20 showed differences in pooled effect estimates. Reviews containing a greater number of primary studies evaluated quality less frequently than smaller reviews. Overall, the majority of reviews evaluated bias; however, many applied questionable methods. Given the potential effects of bias on summary outcomes, greater attention is warranted.

Heterogeneity among the primary studies included in a systematic review (SR) is one of the most challenging considerations for systematic reviewers. Current practices in anaesthesiology SRs have not been evaluated, but traditional methods may not provide sufficient information to evaluate the true nature of these differences. We address these issues by examining the practices for evaluating heterogeneity in anesthesiology reviews. Also, we propose a mapping method for presenting heterogeneous aspects of the primary studies in SRs.We evaluated heterogeneity practices reported in SRs published in highly ranked anesthesiology journals and Cochrane reviews. Elements extracted from the SRs included heterogeneity tests, models used, analyses conducted, plots used, and I2 values. Additionally, we selected a SR to develop an evidence map in order to display clinical heterogeneity.Our statistical analysis showed 150/207 SRs reporting a test for statistical heterogeneity. Plots were used in 138 reviews to display heterogeneity. Subgroup analyses were the most commonly reported analysis (54%). Meta-regression and sensitivity analyses were used sparingly (25%; 23% respectively). A random effects model was most commonly reported (33%). Heterogeneity statistics across meta-analyses suggested that, in our sample, the majority (55%) did not present sufficient heterogeneity to be of great concern. Cochrane reviews (n=58) were also analysed. Plots were used in 88% of Cochrane reviews. Subgroup analysis was used in 59% Cochrane reviews, while sensitivity analysis was used in 62%.Many reviews did not provide sufficient detail regarding heterogeneity. We are calling for improvement to reporting practices.